Electronic apparatus having dual-mode load circuit

ABSTRACT

An electronic apparatus for stably driving a load circuit having operating modes that are vastly different in consumed electric current values and current variations. A supply device supplies a first power. A voltage converting circuit produces a converted power by converting the first power. A control circuit outputs a control signal for controlling the voltage converting circuit and outputting a fourth power based on the converted power. The load circuit is driven by the fourth power and has first and second operating modes and outputs an operating mode signal to the control circuit indicating in which mode it is being operated. The control circuit has first and second output voltage control modes and selects in which of the first and second output voltage control modes an output voltage of the voltage converting circuit is controlled by the operating mode signal.

BACKGROUND OF THE INVENTION

The present invention relates to an electronic apparatus having avoltage converting circuit for converting the voltage of power suppliedby an electricity supply device and operated by power outputted fromthis voltage converting circuit.

FIG. 12 typically shows the schematic construction of a conventionalelectronic apparatus. As shown in FIG. 12, the conventional electronicapparatus is constructed by a voltage converting circuit 702, a controlcircuit 105 and a load circuit 104. The voltage converting circuit 702outputs fourth power 109 by converting the voltage of first power 106supplied from an electricity supply device 101. The control circuit 105detects the voltage of second power and outputs a control signal 710 tocontrol an operation of the voltage converting circuit 702 such that thefourth power 109 has a predetermined desirable voltage. The load circuit104 is operated by the fourth power 109.

In the conventional electronic apparatus having the above construction,the control circuit 105 must be operated in an output voltage controlmode having a large consumed electric current but a high control speedat any time so as to follow a variation of a consumed electric currentof the load circuit 104. Therefore, when there is a period in whichthere is almost no variation of the consumed electric current in theload circuit 104, the control circuit 105 is operated in the outputvoltage control mode although no high control speed is required.Therefore, in this case, a problem exists in that the conversion fromthe first power 106 to the fourth power greatly becomes worse, and nofirst power 106 from the electricity supply device 101 can beeffectively utilized to operate the load circuit 104.

Further, the voltage converting circuit 702 is limited in a power rangeable to efficiently output the fourth power 109 from the first power106. Therefore, in the case of a circuit in which consumed power of theload circuit 104 is extremely changed, there is a case in which poweroutside the power range able to efficiently output power by the voltageconverting circuit 702 is supplied to the load circuit 104. In thiscase, a problem exists in that no first power 106 from the electricitysupply device 101 can be effectively utilized to operate the loadcircuit 104.

Such a problem is caused particularly when the load circuit 104 is an IChaving an operating mode having a large consumed electric current and aviolent variation of the consumed electric current, and a standby modehaving a small consumed electric current and a small variation of theconsumed electric current, and is an IC for a portable telephone havinga receiving-transmitting mode having a large consumed electric currentand a violent variation of the consumed electric current, and a waitingmode having a small consumed electric current and a small variation ofthe consumed electric current. The number of cases adopting the IC ofsuch a type in the load circuit 104 is recently increased, and thenumber of cases causing the above problem is increased in recent years.

The above problem becomes particularly serious in a compact portableapparatus having the same construction as the conventional electronicapparatus of the construction shown in FIG. 12. This is because abattery or a secondary battery as the electricity supply device is madecompact and is reduced in capacity as the portable apparatus is madecompact and light in weight, but the load circuit consumes high power toraise functions and is difficult to perform an operation for a long timeand cannot be further operated for a long time when the above problem iscaused.

Further, in a recent compact portable apparatus, it is necessary to makethe secondary battery as the electricity supply device compact and lightin weight and increase capacity of the secondary battery so as to makethe portable apparatus compact and light in weight and raise performanceof the portable apparatus and operate the portable apparatus for a longtime. Therefore, the type of a high battery voltage tends to be adoptedin the secondary battery. In contrast to this, the load circuit of thecompact portable apparatus tends to adopt an IC constructed by a MOSFETof a fine structure at the sacrifice of a withstand voltage with respectto the voltage of the load circuit, and a MOSFET having a fine and SOIstructure at the sacrifice of a withstand voltage with respect to thevoltage of the load circuit so as to reconcile high performance and lowconsumed power. Therefore, in a recent compact portable apparatus, noload circuit can be directly operated by power of the battery or thesecondary battery. Accordingly, similar to the construction of theconventional electronic apparatus shown in FIG. 12, the compact portableapparatus increasingly has a construction in which the power of a highvoltage of the secondary battery is converted to power of a low voltageby the voltage converting circuit, and the load circuit is operated bythis converted power of a low voltage. Accordingly, the above problembecomes serious in the recent compact portable apparatus.

Further, in the recent compact portable apparatus, the load circuit alsotends to adopt an IC having a large difference in the consumed electriccurrent and the consumed electric current variation such as theoperating mode and the standby mode, or the receiving-transmitting modeand the waiting mode, etc. to improve performance and reduce powerconsumption. Therefore, the above problem becomes more serious.

SUMMARY OF THE INVENTION

Therefore, a main object of the present invention is to provide anelectronic apparatus in which a load circuit having an operating modeextremely different in a consumed electric current and a consumedelectric current variation can be efficiently operated by convertedpower from the electricity supply device.

In a first construction of an electronic apparatus in the invention, theelectronic apparatus comprises electricity supply device for supplyingpower; a voltage converting circuit for converting the power toconverted power different in voltage from the power and outputting theconverted power; a control circuit for controlling an operation of thevoltage converting circuit such that the converted power becomespredetermined desirable power; and a load circuit operated by theconverted power; wherein the control circuit has a first output voltagecontrol mode and a second output voltage control mode having a consumedelectric current smaller than that in the first output voltage controlmode; the load circuit has a first operating mode and a second operatingmode having a variation of the consumed electric current smaller thanthat in the first operating mode; and the electronic apparatus has aperiod for operating the control circuit in the second output voltagecontrol mode when the load circuit is set to the second operating mode.In accordance with such a construction, it is possible to solve areduction in utilization efficiency of the power of the electricitysupply device 101 with respect to the load circuit 104 as a problem in aperiod in which no consumed electric current of the load circuit 104 isalmost varied.

Further, the load circuit outputs an operating mode signal for notifyingin which of the first and second operating modes the loading circuit isoperated. In accordance with such a construction, in addition to theeffects of the above construction, the operating mode of the loadcircuit can be reliably known so that control can be more reliablyperformed and power can be stably supplied to the load circuit.

Further, the electronic apparatus further comprises electric currentdetecting device in a power supply path from the electricity supplydevice to the load circuit, and the electric current detecting meansjudges in which of the first and second operating modes the load circuitis operated on the basis of electric current detecting results, andoutputs an operating mode signal for notifying the operated operatingmode of the load circuit. In accordance with such a construction, theoperating mode of the load circuit can be reliably known so that controlcan be more reliably performed. Further, power can be stably supplied tothe load circuit, and there is also an effect in that a load circuitexcept for the load circuit able to output the operating mode signal canbe adopted.

Further, the electric current detecting device has electric currentdetecting values at two levels between a first consumed electric currentvalue in the operation of the load circuit in the first operating modeand a second consumed electric current value in the operation of theload circuit in the second operating mode, and the electric currentdetecting device outputs a signal judged as a switching period of thefirst and second operating modes by the load circuit as the operatingmode signal in a detecting period of the electric current value betweenthe electric current detecting values at the two levels. In accordancewith such a construction, in addition to the effects of the aboveconstruction, closer control can be performed, and power can be stablysupplied to the load circuit.

Further, an electronic apparatus comprises electricity device forsupplying first power; a first voltage converting circuit for outputtingsecond power different in voltage from the first power on the basis ofthe first power; a second voltage converting circuit for outputtingthird power different in voltage from the first power on the basis ofthe second power; and a load circuit operated by fourth power based onthe second power and the third power; wherein the first voltageconverting circuit has high power supply ability in comparison with thesecond voltage converting circuit; the second voltage converting circuithas high conversion efficiency in comparison with the first voltageconverting circuit at a supply time of low power; the load circuit hasat least a first operating mode and a second operating mode having avariation of a consumed electric current smaller than that in the firstoperating mode; and the electronic apparatus has a period for generatingthe fourth power based on the second power in the first operating modeof the load circuit, and generating the fourth power based on only thethird power by stopping an operation of the first voltage convertingcircuit in the second operating mode of the load circuit. In accordancewith such a construction, it is possible to solve a reduction inutilization efficiency of the power of the electricity supply device 101with respect to the load circuit as a problem in a small period of theconsumed electric current of the load circuit 104.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a schematic circuit of an electronicapparatus showing a first embodiment of the present invention;

FIG. 2 is a block diagram of a schematic circuit of an electronicapparatus showing a second embodiment of the invention;

FIG. 3 is a diagram of a differential amplifying circuit and itsperipheral circuit used in a control circuit 105 of the electronicapparatus in the invention;

FIG. 4 is a block diagram of a schematic circuit of an electronicapparatus showing a third embodiment of the invention;

FIG. 5 is a block diagram of a schematic circuit of an electronicapparatus showing a fourth embodiment of the invention;

FIG. 6 is a circuit block diagram showing a concrete construction of theelectronic apparatus in the third embodiment of the invention;

FIG. 7 is a circuit diagram showing a first voltage lowering circuitshown in FIG. 6;

FIG. 8 is a circuit diagram showing a second voltage lowering circuitshown in FIG. 6;

FIG. 9 is a circuit block diagram showing a concrete construction of theelectronic apparatus in the fourth embodiment of the invention;

FIG. 10 is a block diagram of a schematic circuit of an electronicapparatus showing a fifth embodiment of the invention;

FIG. 11 is a block diagram of a schematic circuit of an electronicapparatus showing a sixth embodiment of the invention; and

FIG. 12 is a block diagram of a schematic circuit showing an electronicapparatus having a conventional construction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment modes of the present invention will next be explained onthe basis of the drawings.

FIG. 1 is a schematic block diagram of an electronic apparatus in afirst embodiment of the invention. As shown in FIG. 1, the electronicapparatus in the invention has an electricity supply device 101 forsupplying first power 106, a voltage converting circuit 130 foroutputting converted power 121 obtained by converting a voltage of thefirst power 106, a control circuit 105 and a load circuit 104. Thecontrol circuit 105 outputs a control signal 122 for controlling anoperation of the voltage converting circuit 130 and also outputs fourthpower 109 on the basis of the inputted converted power 121. The loadcircuit 104 is operated by the fourth power 109. The load circuit 104has at least first and second operating modes, and outputs an operatingmode signal 112 for transmitting in which of the first and secondoperating modes the load circuit 104 is operated to the control circuit105. The control circuit 105 has first and second output voltage controlmodes, and selects in which of the first and second output voltagecontrol modes an output voltage of the voltage converting circuit 130 iscontrolled by the operating mode signal 112. Here, in the first outputvoltage control mode, a consumed electric current required for controlis large, but a control speed is high. In the second output voltagecontrol mode, the consumed electric current required for control issmall, but the control speed is low. The first operating mode is anoperating mode in which the consumed electric current is increased andis violently varied. The second operating mode is an operating mode inwhich the consumed electric current is reduced and is not almost varied.

When the above construction is used, the output voltage control mode ofthe control circuit 105 can be selected in accordance with the operatingmode of the load circuit 104. Accordingly, when the load circuit 104 isset to the second operating mode, the control circuit 105 canefficiently utilize the first power 106 outputted from the electricitysupply device 101 in the operation of the load circuit 104 by selectingthe second output voltage control mode. Further, when the load circuit104 is set to the first operating mode and switches the first and secondoperating modes, the fourth power 109 having a small voltage variationcan be supplied to the load circuit 104 by selecting the first outputvoltage control mode.

The voltage converting circuit 130 may be a voltage converting circuitof a type using a transformer and a piezo element, a type using a coil,or a type using a capacitor. Further, if only the voltage is lowered,the voltage converting circuit 130 may be also a voltage loweringcircuit of a series regulator type using a resistor and a MOSFET. If theload circuit 104 is a circuit of a consumed electric current such as anIC for a portable telephone, the voltage converting circuit of aswitching regulator system using a coil is most suitable in compactnessand high conversion efficiency. However, when power consumption of theload circuit 104 is low, the voltage converting circuit of a capacitortype is most suitable in further compactness and high convertingefficiency. If the power consumption of the load circuit 104 is low andonly the voltage is lowered, the voltage lowering circuit of a seriesregulator type using a resistor and a MOSFET is most suitable.

When the load circuit 104 is set to an IC for a portable telephone as anexample, the consumed electric current tends to be increased and thevariation of the consumed electric current tends to be violent atreceiving and transmitting times in the first operating mode of the ICfor a portable telephone. Accordingly, the control circuit 105 selectsthe first output voltage control mode. In this first output voltagecontrol mode, a comparator circuit, an error amplifier, a bleederresistor, etc. required in the control circuit 105 are preferablyoperated at high speeds in comparison with the second output voltagecontrol mode. The consumed electric current is small and the variationof the consumed electric current is small at a waiting time in thesecond operating mode of the IC for a portable telephone. Accordingly,the control circuit 105 selects the second output voltage control mode.In this second output voltage control mode, the consumed electriccurrent is preferably reduced instead of a high speed operation byreducing electric currents of the comparator circuit, the erroramplifier, the bleeder resistor, etc. required in the control circuit105, and performing an intermittent operation.

Further, the operating mode signal 112 from the load circuit 104 ispreferably set to a signal for transmitting a change in the operatingmode of the load circuit 104 before the operating mode is changed. Thereasons for this are as follows. When no operating mode of the loadcircuit 104 can be known in advance and the control circuit 105 isoperated in the second output voltage control mode and the operatingmode of the load circuit 104 is changed to the first operating mode, itis impossible to cope with a load variation in this case so that theoutput voltage of the voltage converting circuit 130 is varied.Therefore, various problems of an error in the operation of the loadcircuit 104, and breakdown of the load circuit 104 in a serious case ofthe voltage variation are caused. Namely, a stable operation of the loadcircuit 104 can be performed by knowing the operating mode of the loadcircuit 104 in advance.

FIG. 2 is a schematic block diagram of an electronic apparatus in asecond embodiment of the invention.

This embodiment differs from the first embodiment shown in FIG. 1 asfollows. Namely, in the first embodiment, the operating mode signal 112is outputted from the load circuit 104. However, in the secondembodiment, the operating mode signal 112 is not outputted from the loadcircuit 104, but is outputted from an electric current detecting device120 newly arranged from the control circuit 105 to a power supply pathof the load circuit 104. The second embodiment has the same constructionas the first embodiment with respect to the remaining portions. Namely,in the second embodiment shown in FIG. 2, the consumed electric currentof the load circuit 104 is detected by the electric current detectingdevice 120 so that it is judged in which operating mode the load circuit104 is operated. The operating mode signal 112 based on results of thisjudgment is outputted.

In accordance with the above construction, the load circuit 104 islimited to a circuit able to output the operating mode signal 112 in thefirst embodiment having the construction shown in FIG. 1, but it is alsopossible to cope with the situation by the load circuit 104 unable tooutput the operating mode signal 112 in the construction of the secondembodiment shown in FIG. 2. However, since no operating mode of the loadcircuit 104 can be known in advance, there are possibilities of an errorin the operation and breakdown of the load circuit 104 in switching ofthe operating mode of the load circuit 104 as mentioned above.Accordingly, the load circuit 104 adopts a type in which the consumedelectric current in the switching of the operating mode is graduallyincreased or decreased. The electric current detecting device 120detects two consumed electric current levels constructed by a firstconsumed electric current slightly smaller than the consumed electriccurrent in the operation of the load circuit 104 in the first operatingmode, and a second consumed electric current slightly greater than theconsumed electric current in the operation of the load circuit 104 inthe second operation mode. At this time, when the consumed electriccurrent of the load circuit 104 is equal to or greater than the firstconsumed electric current, it is judged that the load circuit 104 isoperated in the first operating mode. In contrast to this, when theconsumed electric current of the load circuit 104 is smaller than thesecond consumed electric current, it is judged that the load circuit 104is operated in the second operating mode. When the consumed electriccurrent of the load circuit 104 is smaller than the first consumedelectric current and is equal to or greater than the second consumedelectric current, it is judged that the load circuit 104 is in anintermediate switching state of the operating mode, and the electriccurrent detecting device 120 preferably outputs the operating modesignal 112 based on results of this judgment. The control circuit 105can select an optimum control mode at an initial stage of the switchingof the operating mode of the load circuit 104 by adopting such aconstruction. Accordingly, a driving voltage variation of the loadcircuit 104 can be prevented and an error in the operation and breakdownof the load circuit 104 can be prevented.

The electric current detecting device 120 may be any device if thisdevice can detect an electric current amount. However, a device forarranging a resistor element and flowing a detecting electric currentthrough the resistor element and detecting the electric current amountby the magnitude of a voltage generated at both ends of the resistorelement is preferable since this device can be simplified in structure.

FIG. 3 is a diagram of a differential amplifying circuit and itsperipheral circuit used in the control circuit 105 shown in the firstand second embodiments. The differential amplifying circuit and itsperipheral circuit are constructed by a converted power input terminal811, a first bleeder resistor, a second bleeder resistor, a first switchelement 814, a second switch element 813, a differential amplifyingcircuit 801, an electric current variable circuit 803, a VREF circuit223, a switching circuit 804, an amplifying signal output terminal 802and an operating mode input terminal 810. Converted power 121 shown inthe first and second embodiments is inputted to the converted powerinput terminal 811. The first bleeder resistor is constructed byresistors 806 and 808. The second bleeder resistor is constructed byresistors 805 and 807. The electric current variable circuit 803 adjustsa bias electric current of the differential amplifying circuit 801. TheVREF circuit 223 generates a reference voltage. The switching circuit804 controls electric current paths of the first and second bleederresistors to a GND terminal. The amplifying signal output terminal 802outputs an output signal of the differential amplifying circuit 801. Theoperating mode signal 112 shown in the first and second embodiments isinputted to the operating mode input terminal 810. The voltage of theconverted power inputted from the converted power input terminal 811 isdivided by the first or second bleeder resistor. The difference betweenthe divided voltage and the reference voltage outputted from the VREFcircuit 223 is amplified by the differential amplifying circuit 801 andis outputted to the amplifying signal output terminal 802.

The electric current variable circuit 803 is a circuit for switching thefirst and second output voltage control modes of the control circuit 105described in the first and second embodiments. The first and secondoutput voltage control modes are switched by switching the bias electriccurrent of the differential amplifying circuit 801 in accordance withthe operating mode signal inputted from the operating mode signal inputterminal 810. The bias electric current is larger in the first outputvoltage control mode, and is smaller in the second output voltagecontrol mode. Further, as the bias electric current is increased, thedifferential amplifying circuit 801 can be operated at a higher speed,but the consumed electric current is increased. Therefore, as describedtill now, control speed in the first output voltage control mode isimproved in comparison with the second output voltage control mode, butthe consumed electric current is increased.

Further, the electric current variable circuit 803 has a function forgradually varying the bias electric current. Thus, it is possible torestrain a reduction in precision of the differential amplifying circuit801 as a problem as much as possible when the bias electric current issuddenly varied. This is because the voltage of the fourth power 109shown in FIGS. 1 and 2 is varied when such a reduction in precision iscaused. Namely, the electric current variable circuit 803 can switch thefirst and second output voltage control modes while the electric currentvariable circuit 803 sets the voltage variation of the fourth power 109within a predetermined desirable spec (small range) by gradually varyingthe bias electric current. A variable speed of the bias electric currentcan be increased and changed as a responsive speed of the differentialamplifying circuit 801 is increased. However, it is sufficient to set achanging speed for approximately changing 1 μA in 1 msec.

Furthermore, the electric current variable circuit 803 also has afunction for varying the variable speed of the bias electric current inaccordance with the bias electric current. The variable speed of thebias electric current is controlled in a direction in which the variablespeed of the bias electric current is increased as the bias electriccurrent is increased. This control is performed to improve a precisionrestoring speed of the differential amplifying circuit 801 when the biaselectric current of the differential amplifying circuit 801 isincreased. Therefore, in this case, the above control is performedbecause the precision reduction can be restrained even when the variablespeed of the bias electric current is increased.

Since the electric current variable circuit 803 has the above function,the electric current variable circuit 803 can rapidly switch the firstand second output voltage control modes while the electric currentvariable circuit 803 sets the voltage variation of the fourth power 109within the predetermined desirable speck. Accordingly, it is possible toreduce a time loss due to this switching time.

In contrast to this, the switching circuit 804 controls the electriccurrent paths of the first and second bleeder resistors to the GNDterminal in accordance with the operating mode signal inputted from theoperating mode signal input terminal 810. The switching circuit 804outputs a switching signal 812 for controlling turning-on andturning-off of the first switch element 814 and the second switchelement 813. The first switch element 814 controls the supply of thevoltage divided by the first bleeder resistor to the differentialamplifying circuit 801. The second switch element 813 controls thesupply of the voltage divided by the second bleeder resistor to thedifferential amplifying circuit 801.

Voltage dividing ratios of the first and second bleeder resistors areequal, and a resistance value of the resistor 806 constituting the firstbleeder resistor is smaller than a resistance value of the resistor 805constituting the second bleeder resistor. Accordingly, a follow-upproperty with respect to the voltage variation of the converted powerinput terminal 811 is preferable but the consumed electric current islarge in characteristics of the voltage divided by the first bleederresistor in comparison with the voltage divided by the second bleederresistor. It is preferable to use the first bleeder resistor in thefirst output voltage control mode, and use the second bleeder resistorin the second output voltage control mode.

The switching circuit 804 also has a function for arranging an electriccurrent path to the GND terminal in only one of the bleeder resistorsafter the electric current path to the GND terminal is arranged in boththe bleeder resistors in the switching of the first and second bleederresistors. Since such a function is provided, a value of the dividedvoltage inputted to the differential amplifying circuit 801 becomesindefinite in the switching of the bleeder resistors, and it is possibleto prevent that no control circuit 105 shown in FIGS. 1 and 2 cancontrol the voltage of the fourth power 109 shown in FIGS. 1 and 2.

The control circuit 105 can have the first and second output voltagecontrol modes, and the voltage variation of the fourth power 109 causedin the switching of the first and second output voltage control modescan be restrained within a predetermined desirable speck by using thedifferential amplifying circuit and its peripheral circuit having theabove construction and function in the control circuit 105 in each ofthe embodiments shown in FIGS. 1 and 2. Further, the switching speed isincreased and a time loss due to this switching is reduced.

FIG. 4 is a schematic block diagram of an electronic apparatus in athird embodiment of the invention.

As shown in FIG. 4, the electronic apparatus in this embodiment has anelectricity supply device 101 for supplying first power 106, a firstvoltage converting circuit 102 for outputting second power 107 obtainedby converting a voltage of the first power 106, a second voltageconverting circuit 103 for outputting third power 108 obtained byconverting a voltage of the first power 106, a control circuit 105, anda load circuit 104. The control circuit 105 outputs a first controlsignal 110 for controlling an operation of the first voltage convertingcircuit 102 and a second control signal 111 for controlling an operationof the second voltage converting circuit 103, and also outputs fourthpower 109 on the basis of the inputted second power 107 and the inputtedthird power 108. The load circuit 104 is operated by the fourth power109. Further, the load circuit 104 has a first operating mode havinglarge consumed power, and a second operating mode having consumed powersmaller than that in the first operating mode. The load circuit 104outputs an operating mode signal 112 for transmitting in which of thefirst and second operating modes the load circuit 104 is operated to thecontrol circuit 105. Further, the control circuit 105 can control afirst control signal 110 and a second control signal 111 in accordancewith the operating mode signal 112.

In accordance with the above construction, an optimum method for theoperating mode of the load circuit 104 can be selected from a method forconverting the second power 107 to the fourth power 109, a method forconverting the third power 108 to the fourth power 109, and a method forconverting combined power of the second power 107 and the third power108 to the fourth power 109. Accordingly, the first power 106 outputtedfrom the electricity supply device 101 can be efficiently utilized tooperate the load circuit 104.

The first voltage converting circuit 102 and the second voltageconverting circuit 103 may be a voltage converting circuit having a typeusing a transformer and a piezo element, a type using a coil, and a typeusing a capacitor. Further, when only a voltage is lowered, the firstvoltage converting circuit 102 and the second voltage converting circuit103 may be also a voltage lowering circuit of a series regulator typeusing a resistor and a MOSFET. When the load circuit 104 is a circuit ofa consumed electric current such as an IC for a portable telephone, thevoltage converting circuit of a switching regulator system using a coilis optimal in view of compactness and high conversion efficiency.Further, when the consumed power of the load circuit 104 is low, thevoltage converting circuit of a capacitor type is optimal in view offurther compactness and high conversion efficiency. Further, when theconsumed power of the load circuit 104 is low and only a voltage islowered, the voltage lowering circuit of a series regulator type using aresistor and a MOSFET is optimal.

When the difference in consumed power between the first and secondoperating modes of the load circuit 104 is large and the consumed powerin the second operating mode is extremely small, it is preferable toadopt the voltage converting circuit of the switching regulator systemusing a coil in the first voltage converting circuit 102, and adopt thevoltage converting circuit using a capacitor in the second voltageconverting circuit 103. Further, when the consumed power in both theoperating modes of the load circuit 104 is low and it is sufficient forthe first voltage converting circuit 103 to have a function of only thevoltage lowering, it is preferable to adopt the voltage convertingcircuit using a capacitor in the first voltage converting circuit 102,and adopt the voltage lowering circuit of the series regulator typeusing a resistor and a MOSFET in the second voltage converting circuit103.

The operating mode signal 112 is preferably set to a signal fortransmitting a change in the operating mode of the load circuit 104before the operating mode is changed. This is because the operations ofthe first voltage converting circuit 102 and the second voltageconverting circuit 103 are unstable for a while after starting of theseoperations so that no power can be outputted and no voltage of theoutputted power is set to an object voltage. Namely, when the operatingmode of the load circuit 104 is switched and a stopped voltageconverting circuit is simultaneously operated and the load circuit 104is operated, driving power of the load circuit 104 is insufficient.Therefore, there is a danger that the load circuit 104 is operated inerror and is broken since the driving voltage of the load circuit 104 istoo high. In particular, when the outputted power is small, the secondvoltage converting circuit having high power conversion efficiency isconstructed such that output ability of the power is small. Therefore,when the operating mode of the load circuit 104 is changed to the secondoperating mode having large consumed power from a driving state of theload circuit 104 operated in the second operating mode having smallconsumed power by the power outputted from this second voltageconverting circuit 103, no output power can be obtained from the firstvoltage converting circuit 102 for a while, and the load circuit 104 inthe second operating mode is operated by only the output power from thesecond voltage converting circuit 103. Accordingly, the driving power ofthe load circuit 104 is insufficient during this time, and there is ahigh possibility that the load circuit 104 is operated in error.

Accordingly, the control circuit 105 knows the switching of theoperating mode of the load circuit 104 in advance by the operating modesignal 112. The control circuit 105 operates a voltage convertingcircuit required to be operated in advance, and can set this voltageconverting circuit to a stable operable state before the operating modeof the load circuit 104 is changed. Therefore, it is possible to preventthe driving power of the load circuit 104 from being insufficient and anexcessive voltage from being applied to the load circuit 104 in thechange in the operating mode of the load circuit 104 so that an error inthe operation and breakdown of the load circuit 104 in this case can beprevented.

FIG. 5 is a schematic block diagram of an electronic apparatus inaccordance with a fourth embodiment of the invention.

In the third embodiment, the operating mode signal 112 is outputted fromthe load circuit 104. However, in the fourth embodiment shown in FIG. 5,the operating mode signal 112 is not outputted from the load circuit104, but is outputted from an electric current detecting means 120 newlyarranged from the control circuit 105 to a power supply path of the loadcircuit 104. The fourth embodiment has the same construction as thethird embodiment except for this construction. Namely, in theconstruction of the fourth embodiment, the electric current detectingdevice 120 judges in which operating mode the load circuit 104 isoperated by detecting the consumed electric current of the load circuit104, and outputs the operating mode signal 112 based on results of thisjudgment.

In accordance with the above construction, it is possible to cope withthe situation by the load circuit 104 unable to output the operatingmode signal 112 in the fourth embodiment although the load circuit 104is limited to a circuit able to output the operating mode signal 112 inthe construction of the third embodiment. However, since no operatingmode of the load circuit 104 can be known in advance, there arepossibilities of an error in the operation and breakdown of the loadcircuit 104 in the switching of the operating mode of the load circuit104 as mentioned above. Accordingly, a type for gradually increasing ordecreasing the consumed electric current in the switching of theoperating mode is adopted in the load circuit 104. Further, two consumedelectric current levels constructed by a first consumed electric currentslightly smaller than the consumed electric current in the operation ofthe load circuit 104 in the first operating mode, and a second consumedelectric current slightly greater than the consumed electric current inthe operation of the load circuit 104 in the second operating mode aredetected. When the consumed electric current of the load circuit 104 isequal to or greater than the first consumed electric current, it isjudged that the load circuit 104 is operated in the first operatingmode. In contrast to this, when the consumed electric current of theload circuit 104 is smaller than the second consumed electric current,it is judged that the load circuit 104 is operated in the secondoperating mode. When the consumed electric current of the load circuit104 is smaller than the first consumed electric current and is equal toor greater than the second consumed electric current, it is judged thatthe load circuit 104 is in an intermediate switching state of theoperating mode. The electric current detecting device 120 outputs theoperating mode signal 112 based on results of this judgment. It ispossible to start the operation of the stopped voltage convertingcircuit and stabilize this operation at an initial stage of theswitching of the operating mode of the load circuit 104 by adopting sucha construction. Further, the operated voltage converting circuit can bestopped at a final stage of the switching of the operating mode of theload circuit 104. Therefore, a driving voltage variation of the loadcircuit 104 in the change in the operating mode of the load circuit 104can be prevented, and an error in the operation and breakdown of theload circuit 104 can be prevented.

The electric current detecting device 120 may be any means if this meanscan detect an electric current amount. However, a device for arranging aresistor element and flowing a detected electric current through theresistor element and detecting the electric current amount by themagnitude of a voltage generated at both ends of the resistor element ispreferable since this means can be simplified in structure.

FIG. 6 is a block diagram showing a concrete circuit of the electronicapparatus in the third embodiment of the invention.

As shown in FIG. 6, the electronic apparatus has a battery 201 as anelectricity supply device, a first voltage lowering circuit 202 as afirst voltage converting circuit, a second voltage lowering circuit 203as a second voltage converting circuit, a PWM circuit 207 constituting acontrol circuit, an oscillating circuit 209, a PFM oscillating circuit208, an error amplifier circuit 220, a bleeder resistor constructed by afirst resistor 221 and a second resistor 222, and a VREF circuit 223.

The operations of main constructional circuits will first be explained.The first voltage lowering circuit 202 lowers the voltage of batterypower 205 by switching an internal MOSFET using a first pulse signal 210as a first control signal, and outputs voltage lowering power 206 havinga voltage lower than that of the battery power 205. The second voltagelowering circuit 203 lowers the voltage of the battery power 205 byswitching an internal MOSFET using a second pulse signal 211 as a secondcontrol signal. Similar to the first voltage lowering circuit 202, thesecond voltage lowering circuit 203 outputs voltage lowering power 206having a voltage lower than that of the battery power 205. An IC 204 fora portable telephone is operated by the voltage lowering power 206outputted from the first voltage lowering circuit 202 or the secondvoltage lowering circuit 203, and outputs an operating mode signal 214for transmitting whether the operating mode of the IC 204 is areceiving-transmitting mode or a waiting mode.

The operations of the respective circuits constituting the controlcircuit will next be explained. The voltage of the voltage loweringpower 206 is divided by the first resistor 221 and the second resistor222, and this divided voltage is outputted to a minus input terminal ofthe error amplifier circuit 220. The VREF circuit 223 generates areference voltage, and outputs this reference voltage to a plus inputterminal of the error amplifier circuit 220. The error amplifier circuit220 amplifies the difference between the divided voltage inputted to theminus input terminal and the reference voltage inputted to the plusinput terminal, and outputs results of this amplification as an errorsignal 213. The oscillating circuit 209 outputs a clock signal 212, andperforms control as to whether or not the oscillating circuit 209outputs the clock signal 212 on the basis of an inputted operating modesignal 214. The PWM circuit changes duty of the inputted clock signal212 on the basis of the error signal 213 similarly inputted, and outputsthe clock signal 212 of this changed duty as a first pulse signal 210.Further, the PFM oscillating circuit 208 generates a clock signal of afrequency based on the inputted error signal 213, and outputs this clocksignal as a second pulse signal 211, and performs control as to whetheror not the PFM oscillating circuit 208 outputs the second pulse signal211 on the basis of the inputted operating mode signal 214. When nooscillating circuit 209 outputs the clock signal 212 on the basis of theoperating mode signal 214, no first pulse signal 210 is also outputtedfrom the PWM circuit 207 so that the operation of the first voltagelowering circuit 202 is stopped. Accordingly, no voltage lowering power206 is outputted from the first voltage lowering circuit 202. Further,when no PFM oscillating circuit 208 outputs the second pulse signal 211on the basis of the operating mode signal 214, the operation of thesecond voltage lowering circuit 203 is stopped so that no voltagelowering power 206 is outputted from the second voltage lowering circuit203.

The following operations can be performed by performing the aboveoperation by each circuit of the above construction.

First, even when the consumed electric current of the IC 204 for aportable telephone is varied, the voltage of voltage lowering power 206outputted from the first voltage lowering circuit 202 or the secondvoltage lowering circuit 203 can be controlled such that a voltageobtained by dividing the voltage of the voltage lowering power 206 bythe first resistor 221 and the second resistor 222 is equal to areference voltage generated by the VREF circuit 233. Namely, the voltageof the voltage lowering power 206 can be approximately set to beconstant. Accordingly, the IC 204 for a portable telephone can be stablyoperated by the voltage lowering power 206 held approximately at aconstant voltage.

Next, even when the operating mode of the IC 204 for a portabletelephone is changed and the consumed electric current of the IC 204 fora portable telephone is extremely varied, a method able to mostefficiently utilize the battery power 201 to operate the IC 204 for aportable telephone can be selected from a method for operating the IC204 for a portable telephone by the voltage lowering power 206 outputtedfrom the first voltage lowering circuit 202, a method for operating theIC 204 for a portable telephone by the voltage lowering power 206outputted from the second voltage lowering circuit 203, and a method foroperating the IC 204 for a portable telephone by the voltage loweringpower 206 outputted from both the first voltage lowering circuit 202 andthe second voltage lowering circuit 203. Accordingly, the battery power201 can be efficiently utilized to operate the IC 204 for a portabletelephone so that the portable telephone adopting the construction ofthis embodiment can be operated for a long time.

FIG. 7 is a diagram of the first voltage lowering circuit 202 shown inFIG. 6.

As shown in FIG. 7, the first voltage lowering circuit 202 is a voltagelowering circuit of a switching regulator type using a coil 303. Thevoltage lowering circuit of this type is of a type of high powerconversion efficiency when power lowered in voltage is relatively large.Accordingly, this type is suitable for supply of the voltage loweringpower 206 when the IC 204 for a portable telephone shown in FIG. 6 isoperated in a transmitting-receiving mode and relatively large voltagelowering power is required.

As shown in FIG. 7, the first voltage lowering circuit 202 has a P-typeMOSFET 301, a diode 302, a coil 303, a battery power input terminal 310for inputting the battery power 205 shown in FIG. 6 thereto, a pulsesignal input terminal 312 for inputting a first pulse signal 210thereto, and a voltage lowering power output terminal 311 for outputtingthe voltage lowering power 206. A source electrode and a base electrodeof the P-type MOSFET 301 are connected to the battery power inputterminal, and a gate electrode of the P-type MOSFET 301 is connected tothe pulse signal input terminal 312. A drain electrode of the P-typeMOSFET 301 is connected to a first electrode of the coil 303 and a firstelectrode of the diode 302. A second electrode of the diode 302 isconnected to a GND terminal. A second electrode of the coil 303 isconnected to the voltage lowering power output terminal 311. A forwarddirection of the diode 302 is set to a direction from the secondelectrode of the diode 302 to its first electrode.

In accordance with the above construction, the P-type MOSFET 301 isswitched by the first pulse signal inputted to the pulse signal inputterminal 312 so that the voltage of the battery power inputted to thebattery power input terminal 310 is lowered and this battery powerlowered in voltage can be outputted from the voltage lowering poweroutput terminal 311 as voltage lowering power.

The diode 302 may be any diode if this diode has a rectifying action.However, in this embodiment, a diode able to obtain the rectifyingaction by a simple circuit construction is adopted. Further, the diodeof a Schottky type having a small forward drop voltage may be alsoadopted to reduce power loss due to the forward drop voltage of thediode as much as possible.

FIG. 8 shows a diagram of the second voltage lowering circuit 203 shownin FIG. 6. This second voltage lowering circuit is a voltage loweringcircuit of a type using a capacitor. The voltage lowering circuit ofthis type is of a type of high power conversion efficiency when verysmall voltage lowering power is supplied. Accordingly, it is suitablefor the supply of the voltage lowering power 206 when the IC 204 for aportable telephone shown in FIG. 6 is operated in a waiting mode andonly very small consumed power is required.

As shown in FIG. 8, the voltage lowering circuit of this constructionhas a P-type MOSFET 401, a first N-type MOSFET 402, a second N-typeMOSFET 403, a third N-type MOSFET 404, a first capacitor 405, a secondcapacitor 406 and an inverter circuit 303. Further, a battery powerinput terminal 410 for inputting the battery power 205 shown in FIG. 6thereto, a pulse signal input terminal 411 for inputting the secondpulse signal 211 thereto, and a voltage lowering power output terminal412 for outputting the voltage lowering power 206 are arranged. Further,the pulse signal input terminal 411 is connected to gate electrodes ofthe P-type MOSFET 401, the first N-type MOSFET 402 and the third N-typeMOSFET 404, and is also connected to an input electrode of an invertercircuit 407. An output electrode of the inverter circuit 407 isconnected to a gate electrode of the second N-type MOSFET 403. A sourceelectrode and a base electrode of the P-type MOSFET 401 are connected tothe battery power input terminal, and a drain electrode of the P-typeMOSFET 401 is connected to a first electrode of a first capacitor 405and a drain electrode of the third N-type MOSFET 404. A source electrodeand a base electrode of the first N-type MOSFET 402 are connected to aGND terminal, and a drain electrode of the first N-type MOSFET 402 isconnected to a second electrode of the first capacitor 405 and a drainelectrode of the second N-type MOSFET 403. A source electrode of thesecond N-type MOSFET 403 is connected to a first electrode of a secondcapacitor 406, and second electrodes of the first capacitor 405 and thesecond capacitor 406 are connected to the GND terminal.

In accordance with the above construction, each MOSFET is switched by asecond pulse signal inputted from the pulse signal input terminal 411 sothat a connecting state of each capacitor is switched. Thus, the voltageof the battery power inputted to the battery power input terminal 410 islowered, and this battery power lowered in voltage can be outputted fromthe voltage lowering power output terminal 412 as voltage loweringpower.

The second capacitor 406 also has a function for smoothing power sourceof the IC 204 for a portable telephone shown in FIG. 6.

As mentioned above, in this embodiment, the construction shown in FIG. 6is adopted. The first voltage lowering circuit 202 shown in FIG. 6adopts a voltage lowering circuit of a switching regulator type using acoil as a type in which power conversion efficiency is increased whenrelatively large voltage lowering power as shown in FIG. 7 is outputted.The second voltage lowering circuit 203 shown in FIG. 6 adopts a voltagelowering circuit of a type using a capacitor as a type in which powerconversion efficiency is increased when very small voltage loweringpower as shown in FIG. 8 is outputted. Accordingly, the IC for aportable telephone can be mainly operated by the voltage lowering powerfrom the first voltage lowering circuit in a transmitting-receiving modeof large consumed power of the IC for a portable telephone. The IC for aportable telephone can be mainly operated by the voltage lowering powerfrom the second voltage lowering circuit in a waiting mode of very smallconsumed power of the IC for a portable telephone. Accordingly, incomparison with a case in which the IC for a portable telephone isoperated by the voltage lowering power of one voltage lowering circuitin the conventional construction, power conversion efficiency of thevoltage lowering circuit is improved and the IC for a portable telephonecan be efficiently operated by battery power. Therefore, the portabletelephone adopting the construction of this embodiment can be operatedfor a long time.

Further, in this embodiment, as shown in FIG. 6, the operating modesignal 214 outputted from the IC 204 for a portable telephone isconstructed by a signal for notifying in which of thetransmitting-receiving mode and the waiting mode the IC 204 for aportable telephone is operated in advance, and a signal for notifyingthe operating mode in real time. In accordance with this construction,when the operating mode of the IC 204 for a portable telephone ischanged to the transmitting-receiving mode from the waiting mode forperforming the operation by the voltage lowering power of the secondvoltage lowering circuit 203, the first voltage lowering circuit 202 canbe operated in advance by the operating mode signal 214, and theoperating mode can be set to the transmitting-receiving mode after theoperation of the first voltage lowering circuit 202 is stabilized. Then,the operation of the second voltage lowering circuit 203 can be stopped.Conversely, when the operating mode of the IC 204 for a portabletelephone is changed to the waiting mode from the transmitting-receivingmode for performing the operation by the voltage lowering power of thefirst voltage lowering circuit 202, the operating mode can be set to thewaiting mode after the operation of the second voltage lowering circuit202 is stabilized by operating the second voltage lowering circuit 202in advance. Then, the operation of the first voltage lowering circuit202 can be stopped.

Accordingly, the operating mode of the IC 204 for a portable telephonecan be switched at any time after the operation of a required voltagelowering circuit is stabilized. Therefore, a driving voltage of the IC204 for a portable telephone is stabilized.

However, when the operating mode of the IC 204 for a portable telephoneis changed in the above construction, the driving voltage of the IC fora portable telephone is inevitably slightly varied. This is because anoperating speed of the error amplifier circuit 220 is reduced to preventan oscillating phenomenon as a phenomenon in which the voltages of thevoltage lowering power outputted from both the voltage lowering circuitsare periodically varied. Accordingly, at a changing time of theoperating mode at which the consumed electric current of the IC 204 fora portable telephone is suddenly varied, voltage control of the voltagelowering power outputted from the voltage lowering circuits isinevitably delayed so that the driving voltage of the IC 204 for aportable telephone is varied. Therefore, to remove this variation of thedriving voltage, the IC 204 for a portable telephone preferably adopts atype in which the consumed electric current is gradually changed in thechange in the operating mode.

FIG. 9 is a diagram showing a concrete circuit block in an electronicapparatus in accordance with a fourth embodiment of the invention.

The circuit block diagram shown in FIG. 9 differs from the circuit blockdiagram shown in FIG. 6 in the following points. Namely, in the circuitblock diagram shown in FIG. 6, the operating mode signal 214 isoutputted from the IC 204 for a portable telephone. However, in thecircuit block diagram shown in FIG. 9, the operating mode signal 214 isnot outputted from the IC 204 for a portable telephone, but is outputtedfrom a load electric current detecting circuit 225 arranged between aplus side power source input terminal of the IC 204 for a portabletelephone and a voltage lowering power output terminal of a firstvoltage lowering circuit 202 or a second voltage lowering circuit 203.The other constructions of the circuit block diagram shown in FIG. 9 arethe same as the circuit block diagram shown in FIG. 6. Namely, it isjudged whether the IC 204 for a portable telephone is set to thetransmitting-receiving mode or the waiting mode by detecting theconsumed electric current of the IC 204 for a portable telephone by thisload electric current detecting circuit 225. Results of this judgmentare outputted as the operating mode signal 214.

In accordance with the above construction, the driving power of the IC204 for a portable telephone can be selected from the voltage loweringpower outputted from the first voltage lowering circuit 202, the voltagelowering power outputted from the second voltage lowering circuit 203,and the voltage lowering power outputted from both the voltage loweringcircuits in accordance with the operating mode of the IC 204 for aportable telephone even when the IC 204 for a portable telephone has nofunction able to output the operating mode signal 214.

However, the above contents can be executed, but no change in theoperating mode of the IC 204 for a portable telephone can be known inadvance although this change can be known in the first embodiment.Therefore, the IC 204 for a portable telephone adopts a construction inwhich the consumed electric current is gradually increased or decreasedin the change in the operating mode. Further, the load electric currentdetecting circuit 225 has two levels constructed by first and seconddetecting levels with respect to a detecting level of the consumedelectric current of the IC 204 for a portable telephone. At the firstdetecting level, the consumed electric current of the IC 204 for aportable telephone is slightly smaller than the consumed electriccurrent in the operation of the IC 204 for a portable telephone in thetransmitting-receiving mode. At the second detecting level, the consumedelectric current of the IC 204 for a portable telephone is slightlygreater than the consumed electric current in the operation of the IC204 for a portable telephone in the waiting mode. When the consumedelectric current of the IC 204 for a portable telephone is equal to orgreater than the first detecting level, it is judged that the IC 204 fora portable telephone is operated in the first operating mode. Incontrast to this, when the consumed electric current of the IC 204 for aportable telephone is smaller than the second detecting level, it isjudged that the IC 204 for a portable telephone is operated in thesecond operating mode. When the consumed electric current of the IC 204for a portable telephone is smaller than the first detecting level andis equal to or greater than the second detecting level, it is judgedthat the IC 204 for a portable telephone is in a changing state of theoperating mode. The operating mode signal 214 based on this judgment isoutputted. Further, when the operating mode signal 214 transmits thechanging state of the operating mode of the IC 204 for a portabletelephone, both the voltage lowering circuits are operated by operatingboth the oscillating circuit 209 and the PFM oscillating circuit 208. Incontrast to this, when the operating mode signal 214 transmits theoperation of the IC 204 for a portable telephone in the first operatingmode, only the first voltage lowering circuit 202 is operated bystopping only the PFM oscillating circuit 208. Further, when theoperating mode signal 214 transmits the operation of the IC 204 for aportable telephone in the second operating mode, only the second voltagelowering circuit 203 is operated by stopping only the oscillatingcircuit 209.

In accordance with the above control construction, the operation of arequired voltage lowering circuit is started at an initial changingstage of the operating mode of the IC 204 for a portable telephone.Therefore, the voltage lowering circuit already operated is stablyoperated at a stage at which the operating mode of the IC 204 for aportable telephone has been changed. Accordingly, the variation of thedriving voltage of the IC 204 for a portable telephone can be preventedwhen the operating mode of the IC 204 for a portable telephone ischanged. The driving voltage variation of the IC 204 for a portabletelephone in the change in the operation mode of the IC 204 for aportable telephone can be also prevented by delaying the processingspeed of the error amplifier circuit 220 as mentioned above.

FIG. 10 is a schematic block diagram of an electronic apparatus in afifth embodiment of the invention. An electricity supply device 101, afirst voltage converting means 102, a second voltage converting means103 and a load circuit 104 are constructed by using the same as thethird embodiment. Namely, the electronic apparatus has the electricitysupply device 101 for supplying first power 106, the first voltageconverting circuit 102 for outputting second power 107 obtained byconverting the voltage of the first power 106, and the second voltageconverting circuit 103 for outputting third power 108 obtained byconverting the voltage of the first power 106. Further, the electronicapparatus has a first control circuit 1001, a second control circuit1002, a first variable resistor 1003, a second variable resistor 1004, aload circuit 104 operated by fourth power 109, and a resistor controlcircuit 1005. The first control circuit 1001 monitors the voltage of thesecond power 107, and controls an operation of the first voltageconverting circuit 102 by a first control signal 110 such that thisvoltage becomes a predetermined desirable voltage. The second controlcircuit 1002 monitors the voltage of the third power 108, and controlsan operation of the second voltage converting circuit 103 by a secondcontrol signal 111 such that this voltage becomes a predetermineddesirable voltage. Each of the first control circuit 1001 and the secondcontrol circuit 1002 has the same basic construction and operation asthe control circuit 105 described in the first to fourth embodiments.

The load circuit 104 has at least first and second operating modes, andoutputs an operating mode signal 112 for notifying in which operatingmode the load circuit 104 is operated. The resistor control circuit 1005outputs a first resistor variable signal 1006 and a second resistorvariable signal 1007 in accordance with the operating mode signal 112.The first variable resistor 1003 is arranged in a supply path forconverting the second power 107 to the fourth power 109, and controls asupply amount of the second power 107 by varying a resistance value ofthis first variable resistor 1003 in accordance with the first resistorcontrol signal 1006. The second variable resistor 1004 is arranged in asupply path for converting the third power 108 to the fourth power 109,and controls a supply amount of the third power 108 by varying aresistance value of this second variable resistor 1004 in accordancewith the second resistor control signal 1007. Further, the first controlcircuit 1001 controls its own operation in accordance with the operatingmode signal 112, and also controls an operation of the first voltageconverting circuit 102 by the first control signal 110. The secondcontrol circuit 1002 controls its own operation in accordance with theoperating mode signal 112, and also controls an operation of the secondvoltage converting circuit 103 by the second control signal 111.

In accordance with the above construction, similar to the thirdembodiment, a case for most efficiently utilizing the first power 106 tooperate the load circuit 104 can be selected in accordance with theoperating mode of the load circuit 104 from a case for converting thesecond power 107 to the fourth power 109, a case for converting thethird power 108 to the fourth power, and a case for converting both thesecond power 107 and the third power 108 to the fourth power.Accordingly, the first power 106 can be efficiently utilized, and theload circuit 104 can be stably operated.

In this embodiment, the first operating mode of the load circuit 104 isan operating mode in which the consumed electric current is large orviolently varied in comparison with the second operating mode. The firstvoltage converting circuit 102 is a voltage converting circuit in whichoutput electric current ability is good but conversion efficiency is badin the case of a low output electric current in comparison with thesecond voltage converting circuit 103. The first control circuit 1001 isa control circuit in which control speed is high but the consumedelectric current is large in comparison with the second control circuit1002.

Accordingly, when the load circuit 104 is set to the first operatingmode and the operating mode is switched, the first control circuit 1001is operated and the first voltage converting circuit 102 is operated,and resistance of the first variable resistor 1003 is set to be low.Simultaneously, the operation of the second control circuit 1002 isstopped, and the operation of the second voltage converting circuit 103is stopped, and resistance of the second variable resistor 1004 is setto be high. Thus, only the second power 107 is preferably converted tothe fourth power 109. The reasons for this are as follows. When only thethird power 108 is converted to the fourth power 109 in the switching ofthe operating mode of the load circuit 104 and the operation of the loadcircuit 104 in the first operating mode and the consumed electriccurrent of the load circuit 104 is increased, the supplied electriccurrent of the third power 108 becomes insufficient so that the voltageof the fourth power 104 is reduced and no load circuit 104 can beoperated. When the consumed electric current of the load circuit 104 isviolently varied, it is not overtaken in control of the second controlcircuit 1002 so that the voltage of the fourth power 109 is violentlyvaried. Therefore, the load circuit 104 is operated in error and isbroken. Accordingly, it is necessary for the load circuit 104 to notifythe switching of the operating mode to each circuit by the operatingmode signal 112 before the operating mode is switched. Therefore, theload circuit 104 of the invention also has such a function.

When the load circuit 104 is set to the second operating mode, thesecond control circuit 1002 is operated and the second voltageconverting circuit 103 is operated, and the resistance of the secondvariable resistor 1004 is set to be low. Simultaneously, the operationof the first control circuit 1001 is stopped and the operation of thefirst voltage converting circuit 102 is stopped, and the resistance ofthe first variable resistor 1003 is set to be high. Thus, only the thirdpower 108 is preferably converted to the fourth power 109. The reasonsfor this are as follows. When only the second power 108 is converted tothe fourth power 109 and the load circuit 104 can be stably operated,the first power 106 supplied by the electricity supply device 101 can bemuch more efficiently utilized to operate the load circuit 104 incomparison with a case in which the load circuit 104 is operated byconverting only the second power 108 to the fourth power 109. Further,when the load circuit 104 is operated in the second operating mode, theconsumed electric current of the load circuit 104 is small even whenonly the second power 108 is converted to the fourth power 109.Therefore, the load circuit 104 can be sufficiently operated by thesupply power of the third power 108, or no consumed electric current ofthe load circuit 104 is almost varied so that it is sufficientlyovertaken in control of the second control circuit 1002. Therefore, novoltage of the fourth power 109 is varied and the load circuit 104 canbe stably operated.

When the first variable resistor 1003 is switched from high resistanceto low resistance, the electronic apparatus has a function for operatingthe first voltage converting circuit 102 by operating the first controlcircuit 1001 in advance, and performing the switching after the voltageof the second power 107 attains a stable state. Similarly, when thesecond variable resistor 1004 is switched from high resistance to lowresistance, the electronic apparatus has a function for operating thesecond voltage converting circuit 103 by operating the second controlcircuit 1002 in advance, and performing the switching after the voltageof the third power 108 attains a stable state. The reasons for this areas follows. The voltage of the second power 107 or the third power 108is unstable when the first voltage converting circuit 102 begins to beoperated by operating the first control circuit 1001, or the secondvoltage converting circuit 103 begins to be operated by operating thesecond control circuit 1002. When the first variable resistor 1003 orthe second variable resistor 1004 is switched from high resistance tolow resistance in this unstable state, the voltage of the fourth power109 becomes unstable, and the load circuit 104 is operated in error.

Further, the first variable resistor 1003 and the second variableresistor 1004 are switched from high resistance to low resistance, orlow resistance to high resistance by the first resistor variable signal1006 or the second resistor variable signal 1007 from the resistorcontrol circuit 1005. In this case, the electronic apparatus has afunction for performing the switching by gradually changing a resistancevalue. The reasons for this are as follows. When the resistance value ofthe first variable resistor 1003 or the second variable resistor 1004 issuddenly switched, it is not overtaken in control of the first controlcircuit 1001 or the second control circuit 1002 by a sudden outputelectric current in this case so that the voltage of the second power107 or the third power 108 is varied. As a result, the voltage of thefourth power 109 is varied so that the load circuit 104 is operated inerror and is broken.

FIG. 11 is a schematic block diagram of an electronic apparatus in asixth embodiment of the invention. An electricity supply device 101, afirst voltage converting means 102, a second voltage converting means103, a load circuit 104 and an electric current detecting means 120 areconstructed by using the same as the fourth embodiment. In the fifthembodiment, the operating mode signal 112 is outputted from the loadcircuit 104. However, in the sixth embodiment shown in FIG. 11, theoperating mode signal 112 is not outputted from the load circuit 104,but is outputted from the electric current detecting means 120 newlyarranged between a control circuit 105 and a power supply path of theload circuit 104. The other constructions are similar to those in thefourth embodiment. Namely, in the fourth embodiment, it is judged inwhich operating mode the load circuit 104 is operated by detecting theconsumed electric current of the load circuit 104 by the electriccurrent detecting means 120. The operating mode signal 112 based onresults of this judgment is outputted.

In the construction of the fifth embodiment, the load circuit 104 islimited to a circuit able to output the operating mode signal 112.However, in the sixth embodiment, it is possible to cope with thesituation by the load circuit 104 unable to output the operating modesignal 112 by using the above construction. However, no operating modeof the load circuit 104 can be known in advance. Accordingly, asmentioned above, there are possibilities that the load circuit 104 isoperated in error and is broken in the switching of the operating modeof the load circuit 104. Therefore, the load circuit 104 adopts a typefor gradually increasing or decreasing the consumed electric current inthe switching of the operating mode. The electric current detectingmeans 120 detects two consumed electric current levels of first andsecond consumed electric currents. The first consumed electric currentis slightly smaller than the consumed electric current in the operationof the load circuit 104 in the first operating mode. The second consumedelectric current is slightly greater than the consumed electric currentin the operation of the load circuit 104 in the second operating mode.When the consumed electric current of the load circuit 104 is equal toor greater than the first consumed electric current, it is judged thatthe load circuit 104 is operated in the first operating mode. When theconsumed electric current of the load circuit 104 is smaller than thesecond consumed electric current, it is judged that the load circuit 104is operated in the second operating mode. When the consumed electriccurrent of the load circuit 104 is smaller than the first consumedelectric current and is equal to or greater than the second consumedelectric current, it is judged that the load circuit 104 is in anintermediate switching state of the operating mode. The electric currentdetecting means 120 preferably outputs the operating mode signal 112based on results of this judgment. The operation of each circuitdescribed in the fifth embodiment can be performed by adopting such aconstruction so that a driving voltage variation of the load circuit 104in the switching of the operating mode of the load circuit 104 can beprevented an error in the operation and breakdown of the load circuitcan be prevented.

In accordance with the invention, the electronic apparatus isconstructed by the electricity supply device for supplying power, thevoltage converting circuit for outputting power obtained by converting avoltage of the power from the electricity supply device, and the loadcircuit operated by the power outputted from the voltage convertingcircuit and violently varied in the consumed electric current. In hiselectronic apparatus, the power from the electricity supply device canbe efficiently utilized to operate the load circuit, and an error in theoperation and breakdown of the load circuit can be prevented.

What is claimed is:
 1. An electronic apparatus comprising: anelectricity supply device for supplying power; a voltage convertingcircuit for converting the supplied power into a converted power havinga different voltage from the supplied power, and outputting theconverted power; a control circuit for controlling the voltageconverting circuit such that the converted power has a predeterminedvalue; and a load circuit driven by the converted power; wherein thecontrol circuit has a first output voltage control mode and a secondoutput voltage control mode, the second output voltage control modehaving a consumed electric current smaller than that of the first outputvoltage control mode and a slower control speed than that of the firstoutput voltage control mode; the load circuit has a first operating modeand a second operating mode, the second operating mode having a consumedelectric current smaller than that of the first operating mode; and thecontrol circuit operates in the second output voltage control mode whenthe load circuit is in the second operating mode.
 2. An electronicapparatus according to claim 1; wherein the load circuit outputs anoperating mode signal for indicating in which of the first and secondoperating modes the load circuit is being operated.
 3. An electronicapparatus according to claim 1; further comprising an electric currentdetecting device interposed in a path between the electricity supplydevice and the load circuit for judging in which of the first and secondoperating modes the load circuit is being operated on the basis of adetected electric current, and outputting an operating mode signalindicating the operating mode of the load circuit.
 4. An electronicapparatus according to claim 3; wherein the electric current detectingdevice has electric current detecting values at two levels between afirst consumed electric current value associated with operation of theload circuit in the first operating mode and a second consumed electriccurrent value associated with operation of the load circuit in thesecond operating mode, and the electric current detecting device outputsas the operating mode signal a signal indicating that the load circuitis switching between the first and second operating modes when thedetected electric current value is between the electric currentdetecting values at the two levels.
 5. An electronic apparatus accordingto claim 1; wherein the voltage converting circuit comprises a firstvoltage converting circuit for converting the supplied power to a secondpower having a different voltage from the supplied power and outputtingthe second power, and a second voltage converting circuit for convertingthe supplied power to a third power having a different voltage from thesupplied power, and outputting the third power; and wherein the loadcircuit is operated by a fourth power obtained by the second power andthe third power, the first voltage converting circuit has a high powersupply ability in comparison with the second voltage converting circuit,the second voltage converting circuit has a high conversion efficiencyin comparison with the first voltage converting circuit at a supply timeof low power, and the electronic apparatus generates the fourth powerbased on the second power in the first operating mode of the loadcircuit, and generates the fourth power based on only the third power bystopping the first voltage converting circuit in the second operatingmode of the load circuit.
 6. An electronic apparatus according to claim1; wherein the control circuit operates in the first output voltagecontrol mode when the load circuit is in the first operating mode.
 7. Anelectronic apparatus according to claim 1; wherein the electricitysupply device comprises a battery.
 8. An electronic apparatus accordingto claim 1; wherein the voltage converting circuit selectively lowersthe voltage of the supplied power.
 9. An electronic apparatus accordingto claim 1; wherein the load circuit comprises a cellular telephone IC.10. An electronic apparatus according to claim 9; wherein the operatingmode signal output by the cellular telephone IC indicates whether thecellular telephone is in the first operating mode comprising atransmitting-receiving mode or the second operating mode comprising awaiting mode.
 11. An electronic circuit comprising: a power source; aload having a first operating mode and a second operating mode whichconsumes less current and has a smaller current variation than the firstoperating mode; a voltage converting circuit connected to the powersource; and a control circuit for controlling the voltage convertingcircuit to convert the voltage of the power source into a desired value,the control circuit having a first output voltage control mode and asecond output voltage control mode which consumes less current and has aslower control speed than the first output voltage control mode, thecontrol circuit being operated in the second output voltage control modewhen the load is operated in the second operating mode.
 12. Anelectronic circuit according to claim 11; wherein the control circuitoperates in the first output voltage control mode when the load is inthe first operating mode.
 13. An electronic circuit according to claim11; wherein the load outputs an operating mode signal for indicating inwhich of the first and second operating modes the load is beingoperated.
 14. An electronic circuit according to claim 11; furthercomprising an electric current detecting device interposed between thepower supply and the load for judging in which of the first and secondoperating modes the load is being operated based on a detected currentvalue in the path.
 15. An electronic circuit according to claim 14;wherein the electric current detecting device has electric currentdetecting values at two levels between a first consumed electric currentvalue associated with operation of the load in the first operating modeand a second consumed electric current value associated with operationof the load in the second operating mode, and the electric currentdetecting device outputs as the operating mode signal a signalindicating that the load is switching between the first and secondoperating modes when the detected electric current value is between theelectric current detecting values at the two levels.
 16. An electroniccircuit according to claim 11; wherein the voltage converting circuitcomprises a first voltage converting circuit for converting the suppliedpower to a second power having a different voltage from the suppliedpower, and a second voltage converting circuit for converting thesupplied power to a third power having a different voltage from thefirst power; and wherein the load is driven by a fourth power obtainedfrom the second power and the third power, the first voltage convertingcircuit has a higher power supplying ability in comparison with thesecond voltage converting circuit and the second voltage convertingcircuit has a high conversion efficiency in comparison with the firstvoltage converting circuit at a supply time of low power, and theelectronic apparatus generates the fourth power based on the secondpower in the first operating mode of the load and generates the fourthpower based on only the third power by stopping the first voltageconverting circuit in the second operating mode of the load.
 17. Anelectronic circuit according to claim 11; wherein the power supplycomprises a battery.
 18. An electronic circuit according to claim 11;wherein the load comprises a cellular telephone IC.
 19. An electronicapparatus according to claim 18; wherein the operating mode signaloutput by the cellular telephone IC indicates whether the cellulartelephone is in the first operating mode comprising atransmitting-receiving mode or the second operating mode comprising awaiting mode.